US3153605A - Exothermic compositions containing boron compounds - Google Patents

Description

United States Patent 3,153,605 EXOTHEC (IUD POSITIONS CONTG BORON CQMPOUNDS Courtland M. Henderson, Xenia, and Richard J. Janowiecki, Dayton, Ohio, assignors to Monsanto Company, a corporation of Delaware No Drawing. Filed Aug. 8, 1962, Ser. No. 215,541 8 Claims. (Cl. 14922) The present invention relates to new compositions and methods to carry out exothermic processes useful in metallurgy.

It is an object of the invention to provide novel exothermic compositions which may be used as additives to improve the internal quality and as-cast surface of metal ingots during the ingot teeming operation in the metals industry. It is a further object of the invention to reduce the common tendency of spattering or splashing of molten metals during the teeming of ingots, thereby decreasing metal oxidation that takes place when molten metals are formed into very small droplets in air during teeming. It is also an object to reduce the frequency of defects in ingot surfaces that result from such splashings. It is a further objective of the invention to produce a solid mold additive which when ignited is easily fluidized or melted to form a molten and thermally insulating flux by its own exothermic heat. The release of heat upon ignition accomplishes the further objective of providing a means for supplying sensible heat to ingots teemed at understandably low temperatures. This molten flux forms a protective blanket which is liquid over the wide range of temperatures encountered in the teeming of molten ferrous metals, and which minimizes metal splash and oxidation of the metal during teeming. Still another objective is to provide a molten slag or flux which dissolves undesired refractory compounds encountered during teeming. Typical refractory compounds, such as the oxides and nitrides of iron, nickel, titanium, chromium, aluminum and silicon, are dissolved during ingot teeming to produce ingots of higher internal quality. A further objective is to fill in cracks, craze lines, holes and similar defects, encountered in the interior surface of used ingot molds, in a manner so as to significantly prolong the life of such molds and to increase ingot-to-end product yields for ferrous and non-ferrous metals and alloys.

Gne of the serious problems faced in large metallurgical plants is that inclusions, harmful to the quality of final metal products, are often encountered. Such inclusions, resulting from oxidation of the molten metal, residue from broken bricks, hot-tops, ceramics and other sources, tend to float on the molten metal during ingot teeming and are frequently deposited on or in the surface and subsurface of the solidified ingot. In addition, such materials frequently are trapped within the core of the ingot during the final stages of solidification. These surface and other type defects result in undesirable stringers of broken or strung out lines of inclusions during rolling of the ingots into bars, strips and sheet metal. Such defects reduce the saleability of the final products.

Another problem besetting large ingot producers of stainless steels as well as low alloy and carbon steels, is that of damage to the ingot molds caused by erosion, abrasion, and thermal stressing of their surfaces during teeming, ingot solidification and stripping operations. Large ingot molds are frequently scrapped because their ingot-forming surfaces have been damaged to the point where holes, crevices and craze marks have become so numerous and large as to seriously alfect the surface and the quality of the as-cast ingot. Large holes in the surface of an ingot mold allow the molten metal to form ears on the final ingot which increase the difficulty of removing the ingots from the molds during stripping. Serious tearing or cracking of the ingot surfaces frequently occur and both ingot molds and ingots must be scrapped when such large ingot ears have been formed through the use of an excessively worn or damaged ingot mold as to prevent removal of the ingot from the mold. The hot workability of most stainless and carbon steels are harmfully affected by the presence of large craze lines and cracks in the interior surface of ingot molds.

Another serious problem occurs when titanium or columbium is used to stabilize stainless steels, such as types 321 or 347. Such stainless alloys are used for producing thin highly polished sheets of metal Where even minute surface flaws detract from their decorative functions and saleability. Serious problems are often encountered in the production of such stainless alloys in that surface defects, known as stringers, are formed in the surface of the as-cast ingot during teeming. Such stringers, consisting of refractory oxides of titania, alumina, silica, chromia and others are frequently impossible to remove by polishing techniques. Prior art has attempted to prevent the formation of these undesirable refractory materials during teeming through the use of various fluxes. Premelted fluxes have also been added to the ingot mold prior to teeming but they required expensive, space consuming equipment and copious quantities of flux. Prior art exothermic mold additives not only failed to remove the undesirable refractory materials but produced large quantities of carbonaceous and toxic smoke, and were unreliable in performance.

In another prior art practice a suitable flux was developed that removed most of the undesirable inclusions in the surface of stainless steel ingots, but this was only accomplished through the use of costly, separate, space consuming, flux premelting equipment located in the ingot teeming area. Space in such areas is at a premium in most ferrous metal plants, and in addition use of a premelted flux involves double handling of ingot molds with increased labor costs and reduced output. Excessive quantities of premelted flux are usually required to minimize difliculties encountered when the premelted flux is partially solidified during occasional and unavoidable process delays before the ingots can be teemed. Once premelted flux has been poured into an ingot mold it is essential that teeming of the ingot occur quickly thereafter. Any delay in teeming usually results in solidification of the premelted flux in the ingot mold, with the result that too much of the sensible heat of the molten stainless or other alloy being teemed is consumed in reheating the solidified flux. When this happens excessive and often intolerable ingot contamination is produced. When unavoidable delays in moving ingot molds, charged with a premelt flux, cause excessive cooling and dirtying of the teemed ingots, entire ingots of expensive stainless and other alloys must be downgraded and frequently scrapped.

The use of the exothermic formulations described herein eliminates the problem encountered with the premelt type fluxes, as the formulations of'this invention release enough thermal energy to more than meet the heat requirements needed to produce an effective molten flux at the start of and during ingot teeming.

Patented Oct. 20, 1964 Prior art exothermic mold additives have employed carbonaceous material such as tar, asphalt, and powdered coke, as a reducing agent in combination with cryolite (AlF -3NaF) as a flux, and sodium or potassium nitrate as an oxidizer. Such compositions produced voluminous and undesirable quantities of carbonaceous and toxic smoke and often created more inclusions than they removed.

Other prior art exothermic mold additive formulations employed various combinations of oxides as oxidizers, calcium-silicon as a reducing material, and basic oxide fluxes; but boron was consistently omitted from all such mold additive compounds because it was believed that boron has deleterious eflects on certain properties of ferrous metals and alloys. The teachings of this invention are in opposition to such prior art and current practices, and show that boron compounds can be used with benefit to treated metals when used in exothermic mold additive formulations.

Whereas, prior art exothermic compositions and products have not been accepted or adapted for use on a large scale due to poor performance, production of excessive and toxic smoke, high costs due to excessive and critical processing requirements, it has now been found that a greatly superior exothermic composition may be provided at relatively low cost to solve the above problems. In the practice of this invention we have found critical combinations of oxidizing agents and reducing agent with boron oxides (such as borax and including the sodium and potassium derivatives of boron oxide) have produced superior results in removing harmful inclusions, minimizing molten metal splashings, providing a protective covering to the molten steel during teeming and minimizing smoke volume during ingot teeming. Further benefits obtained included: cleaner ingots with substantially fewer stringers in the rolled sheet; substantially longer mold life; minimized mold preparation and costs, and, significantly increased ingot-to-end product yields.

The following examples illustrate certain specific embodiments of the present invention.

EXAMPLE 1 Representative exothermic mold additive formulations of several prior art projects are presented in Table 1 where a comparison of their compositions is made with typical formulations of this invention.

Table 1 COMPARISON OF PRIOR ART EXOTHERMIC PRODUCTS WITH FORLIULATIONS OF THIS INVENTION Composition, Weight Percent Formulations,

Components Prior Products Present Invention Cryolite Calcium and Silicon (e.g.,

Caa s)- Ferrosilicon Carbon or asphalt Blast furnace slag Anhydrous sodium borate. Parts of equivalent B 03 per 100 parts by weight of equivalent metal oxides (Fezoa, TiOz, F802- TlO N320) prior to firing Parts of equivalent B20 content per 100 parts by weight calcium and silicon prior to firing The above table shows the use of soda ash, Na CO but the equivalent molar proportion of K is found to be equally effective.

The reducing agent employed in the practice of the present invention is a mixture of calcium and silicon which may be used in various forms as a component of the exothermic compositions. It is essential that the ratio of calcium in the calcium-silicon combination be in the proportion of from 20% by weight to by weight of calcium relative to the calcium and silicon. Such combinations may be supplied as a starting material consisting of mechanical mixtures of elemental calcium and silicon as well as alloys and chemical compounds such as Ca Si all of which are regarded as mixtures in the present patent application. The calcium and/ or silicon may also be obtained from various sources such as ferrosilicon and calcium alloys, although the elemental forms are preferred.

EXAMPLE 2 The range of compositions of this invention that are useful in overcoming the preceding state-of-the-art problems in ingot production, is presented in Table 2. Compositions outside of the range of the formulations of this invention presented in Table 2 are not significantly elfective in minimizing stringer defects and smoke while maximizing ingot quality, ingot-to-end product yield and ingot mold life.

It has been found that greatly superior results are obtained over prior art exothermic rnold additive formulations when ferrous metal ingots are treated in ingot molds with the range of compositions shown in Table 2 for formulations of types E, F and G of this invention. The boron oxide content of these formulations as Well as the ratios of boron oxide to metal oxides, and boron oxide to calcium and silicon prior to their reaction in the molds is critical to their success in improving general quality of the ingots treated, prolonging mold life and increasing ingotto-billet or ingot-to-end product (slabs, ears, sheet, etc.) yields. It is understood that the ratio of equivalent boron oxide (B 0 to metal oxides including those resulting from the oxidation of calcium and silicon, after firing, of the formulations of this invention may be used in place of the B 0 content and its ratio by weight of equivalent B 0 to total metal oxides prior to firing of the formulations. shown in Tables 1 and 2.

Table 2 RANGE OF USEFUL COMPOSITIONS AND RATIOS FOR EXOTHERMIC MOLD ADDITIVES OF THIS INVENTION Range of Compositions, Percent By Weight Components Prior to Firing Most Broad Preferred Preferred TYPE E Ilmenite (essentially FeO'TiOZ) 20-68 23-66 25-64 Soda Ash (Na COg) 12-55 14-50 16-46 Calcium-Silicon (Cassia) 10-40 1-35 10-31 Anhydrous Sodium Borate (NazB4O1) 3. 2-24 3. 2-20 3. 2-18 Parts of equivalent B203 per parts by Wt. equivalent metal oxides 1 2-62 2-45 2-37 Parts of equivalent B 03 per 100 parts by wt. of calcium and silicon 5-166 6-139 7-125 TYPE 1 Titanium Oxide (T102) 8-30 10-25 12-22 Iron Oxide (F9203).-- 12-40 18-38 20-37 Soda Ash (Na2COa). 12-55 14-50 16-46 Calcium-Silicon (Cassia) 10-40 12-36 12-31 Anhydrous Sodium Borate (NazBqOs)- 3. 2-24 3. 2-20 3. 2-18 Parts of equivalent B203 per 100 parts by wt. of equivalent metal oxides 2-62 2-39 2-31 Parts of equivalent 13203 per 100 parts by wt. of calcium and silicon 5-166 6-116 7-104 TYPE c lron Oxide (F9203) 20-55 25-50 25-45 Soda Ash (NazCOs). 12-55 14-55 16-50 Calcium-Silicon (omen) 10-40 12-35 14-30 Anhydrous Sodium Borate (Nazl34O7) 3. 2-24 3. 2-20 3. 2-18 Parts of equivalentB o per 100 parts by wt. of equivalent metal oxides 2-62 2-42 2-37 Parts of equivalent 13203 per 100 parts by wt. of calcium and silicon 5-166 6-116 7-89 1 Any titanium, iron, sodium or potassium compounds, excluding boron-containing compounds, shown in above table.

As illustrated by the information in Table 2, the exothermic mold additive formulations, prior to firing,

must contain a minimum of 3.2 to 24% by weight of anhydrous sodium borate or the equivalent amount of B in the range of above 2 and below 62 parts per 100 parts by weight of mixed oxides, consisting of the equivalent oxides of titanium, iron, and sodium compounds, excluding boron-containing compounds, shown in the table.

The preferred range for the amount of anhydrous sodium borate in the unfired exothermic mold additive formulation is above 3.2% and below 20% by weight, corresponding to the equivalent amount of B 0 in the range of above 2 and below 45 par-ts per 100 parts by weight of mixed oxides, consisting of the equivalent oxides of the titanium, iron, and sodium compounds, excluding boron-containing compounds, shown in Table 2. The most preferred range for the amount of anhydrous sodium borate in the unfired exothermic mold additive formulation is above 3.2% and below 18% by weight, corresponding to the equivalent amount of B 0 in the range of above 2 and below 37 parts per 100 parts by weight of mixed oxides, consisting of the equivalent oxides of the titanium, iron, and sodium compounds, excluding boron-containing compounds, shown in Table 2.

A second important and critical composition requirement for the formulation of efiective exothermic mold additive products of this invention is that the equivalent amount of B 0 per 100 parts by weight of calcium and silicon be in the broad range between 5 and 166. More preferred values for this ratio are between 6 and 139, while the most preferred ratio is between 7 and 125. It should be understood that hydrous potassium borate or the hydrated forms of boron oxide and its sodium or potassium compounds can be substituted for equivalent quantities of anhydrous boron oxide or anhydrous sodium and potassium borate. However, when hydrous borates are used, it is important to dry the final mold additive product at a minimum of 150 C. and to protect it from atmospheric moisture until it is to be added to the mold to minimize hydrogen pick-up by the metal from such moisture.

The proper range of compositions of exothermic mold additives formulations is also shown in Table 2 where the permissible variations in weight percent of each typical component is matched with the above boron oxide per 100 parts of metal oxides and boron oxide per 100 parts of calcium and silicon.

EXAMPLE 3 An example of the relative elfectiveness of the formulations of this invention, as compared to prior art exothermic mold additives is presented in Table 3, Where a comparison of the effect on internal ingot cleanliness and stringer defects of the best prior art formulations and Type E, F and G formulations of this invention is made. The information in Table 3 is based on treating individual ingots of type 321 stainless steel from the same heat with each of the exothermic formulations listed, and comparing the results obtained with those from ingots of the same heat processed in molds treated with a conventional nonexothermic mold coating for control purposes.

The superiority of the formulations E, F and G of this invention over the control ingots and those ingots treated with prior-art exothermic mold additive formulations is clear out. A maximum stringer index of 4 in the final polished sheet is required to permit passing of the 321 sheet product as a premium quality item. Only those ingots treated with Formulae E, F and G meet this specification, thus demonstrating in a very pnactical fashion the significantly more effective dissolving powers of the formulations of this invention for undesirable refractory compounds as compared with present state-of-art formulations.

The control ingots from these heats are also rated at less than premium quality with regard to internal ingot cleanliness and stringer defects, while the products from the ingots treated with formulations E, F and G of Table 1 are rated as premium quality. Stringer indices above 7 require diverting to oif-specification ingots and mean severe downgrading or scrapping of the sheet product from such ingots. As shown in Table 3 formulations E, F and G are characterized by boron oxide per parts by weight of metal oxide and boron oxide per 100 parts by weight calcium-silicon ratios within the range of the ratios of this invention listed in Table 2.

Table 3 COMPARISON OF EFFECT OF EXOTHERMIC MOLD ADDI- TIVES OF PRIOR ART WITH EFFECT OF FORMULATIONS OF THIS INVENTION ON MINIMIZING STRINGERS IN TYPE 321 STAINLESS STEEL Average Boron Boron v Mold Internal Oxide/ Oxide/ Average Formulations Addn, Ingot 100 Parts 100 Parts Stringer from Table 1 Lbs./ Cleanliby Wt. by Wt. Index in Ingot ness Metal Calcium Final Ton Index I Oxides and Sheet 1 Silicon 10 6 '6 11 6 7 8 10 10 9 10 10 8 2 7. 3 19. 8 2 9 1 6. 7 23.1 1 11 1 4. 9 13.1 1 Conventional mold coating for control purposes. 6 6-7 No'rE.- A low index is desired for highest quality on the scale of 1 to 10 A unique advantage obtained in the employment of the present exothermic compositions is that there is an improvement in the randomness of orientation of grains formed at and below the as-cast surface of ferrous ingots with these compositons. It is well known that growth of large grains produced in slowly cooled ingots contributes to undesirable defects, such as cracking of the ingots during subsequent processing. Conventional nor1 exothermic mold coatings and other prior art exothermic type of mold additives have not shown any eifectiveness in overcoming or controlling the formation of grains in ingots to the extent that they are practical. The present exothermic compositions, when applied to the bottom of the empty mold, and then having the molten metal added, react to form a molten glass, containing boron compounds, which, at the temperatures of the molten steel and in the presence of strong reducing agents such as carbon and calcium, yield elemental boron which recombines with dissolved carbon, nitrogen and other elements to produce very fine particle refractory nuclei. These nuclei serve as grain refiners, penetrating the surface of the ingot towards the center of the ingot. In addition to the formation of refractory borides, the surface of the solidified molten glass coating facing the ingot metal is characterized by a multitude of smoothly rounded glassy dimples projecting into the molten steel. The presence of these dimples on the interior surface of the solidified glass coating on the ingot mold contributes to or causes increased randomness of the ingot grains within the first 1020% of the exterior surface of the as-cast ingot. The combination of the dirnpled interior surface of the coating plus the formation of boride neuclei serves to prevent the formation of large grains and improves the hot workability of the ingot during subsequent processing.

EXAMPLE 4 The relative volume of smoke produced when the quantities of exothermic mold additives reported in Table 3 are added to ingot molds during teeming is shown in Table 4. The smokiness index of Table 4 is indicative of the maximum volume of smoke produced, the length of time smoke is evolved during teeming, and whether the smoke is characterized by an obnoxious odor. A minimum rating of zero is considered the highest possible rating, while an index rating of 5 or higher is judged intolerable for use in the teeming pits.

Clearly the degree of smokiness shown in Table 4 for formulations E, F and G, representing formulations of this invention, is an improvement over the best prior art or present state-of-the-art formulations. In the case of Formula E, it is superior even to the smokiness of the conventional non-exothermic, non-boron containing mold coating of the test controls.

Table 4 COLIPARISON OF SMIOKINESS INDEX OF PRIOR ART EXO- THERMIC hIOLD ADDITIVES WITH FORIVIULATIONS OF THIS INVENTION EXAMPLE 5 A series of 93 heats of C 1020 carbon steel is used to evaluate the effect of a typical exothermic mold additive of this invention on mold life and ingot-to-billet yields as compared with the performance of two of the best state-of-the-art, boron oxide-free, exothermic mold additives known and the conventional tar base mold coating ordinarily used in steel plants. Table 5 compares the performance of such prior art, and conventional (tar base) mold coating with a typical formulation of this invention during a series of heats in which two new ingot molds, two used ingot molds and two badly Worn molds are each treated per heat with one of the four exothermic mold additives. A conventional mold coating treatment is used for control purposes. Average mold life, as determined by the maximum number of heats possible in a given mold before such mold is considered unusable, and ingot-to-billet yields are presented in Table 5 for new, used and well worn molds treated with mold additives and with a conventional mold coating. The ingot molds are so arranged during teeming that each of the new molds, each of the used ones and each of the badly worn molds to be treated with the various exothermic and the conventional mold coating techniques is separated from its twin by a mold treated with the other mold additives or coating. The order of teeming of each mold is changed after each heat so that the effect on ingot mold life of being first, middle or last in the teeming order would not distort the results obtained with any particular mold additive or treatment.

Table 5 COMPARISON OF MOLD LIFE AND INGOT-TO-BILLET YIELD OBTAINED WITH A PRIOR ART EXOTHERMIC MOLD ADDI'IIVE, A CONVENTIONAL TAR-BASE MOLD- COATING AND A TYPICAL EXOTHERMIC MOLD ADDI- TIVE FORMULATION OF THIS INVENTION IN TREATING 1020 CARBON STEEL TEST CONDITIONS AND OBSERVATIONS 1. Mold Additive or Treatment 2. Average Number of Heats Possible for Each Mold Additive or Treatment Usingtlie Following:

a. New Molds (2 each used) 83 93 81 b. Used Molds (2 each used; 50

prior heats completed) 35 22 45 91 32 c. Well-worn Molds (2 each used:

95 prior heats completed) 12 3 41 80 4 3. Final ingot-to-billet yield per heat obtained, average percent 84 81 84 90 83 Parts of equivalent boron oxide per parts of wt. of equivalent metal oxides 7. 3

5. Parts of equivalent boron oxide per 100 parts by wt. of calcium and silicon Explanatory Notes:

1 Prior art,-boron oxide-free, exothermic mold additive With formulation presented in Table l.

2 Conventional, boron oxide-free, tar base mold coating with formulation presented in Table 1.

3 Same basic composition as E, but without boron oxide content.

4 Typical exothermic mold additive of this invention with formulation presented in Table 1.

5 Conventional Mold Coating Treatment.

As described in Table 1.

The conventional (tar base) mold coating treatment is considered representative of the best current mold coating in use by the steel industry. Exothermic mold additive A (from Table 1), representative of the best present state-of-the-art formulations, makes no significant improvement in the mold life for used and well worn molds. Exothermic mold additive C (from Table l), representative of the early state-of-the-art formulations, actually has a negative effect on the ingot mold life with both used and well worn ingot molds. Formulation K, identical to formulation B (Table 1) except that it does not contain boron oxide, is included to test the importance of boron oxide and the ratio of equivalent boron oxide per 100 parts by weight of equivalent metal oxides, and the ratio of equivalent boron oxide per 100 parts by weight of calcium and silicon. The results obtained with Formula K are better than those obtained with Formula A but poor when compared with performance results (extended mold life and greater yields) of Formula E. Such results clearly demonstrate the importance of using the boroncontent and ratios stipulated in Table 2 for effective exothermic mold additives since the life of used and well Worn molds treated with Formula E, representative of this invention, is significantly longer than that obtained in molds treated with prior art exothermic mold additives, containing no boron oxide, or with a typical conventional mold coating. At the end of the test series the used and Well-worn molds, treated with Formula E, could be used for many more heats. Such a significant increase in the life of used and well worn ingot molds is unique. Not only is the life of the ingot mold increased, as shown in Table 5, but more importantly, the average ingot-to-billet yield is significantly higher for formulation E of this invention as compared with the yields of the prior-art exothermic formulations and the conventional mold-coating treatment, again demonstrating the effectiveness of the boron-containing formulations of this invention.

Observation of occurrences in the ingot mold during teeming in this test series shows that Formula E rapidly and consistently forms an effective liquid flux coating over the top of the molten metal as it rises in the mold during teeming. Oxidation of the molten metal is thus consistently minimized, thereby reducing the quantities of undesirable refractory oxides below the levels found in ingots treated with formulations A, C, and the conventional mold coating. Coatings formed on the ingot Wall by the use of formulation E are adherent and quickly fill cracks ranging in size from small craze lines to long A" to /2" widths and wide jagged holes from /2 to 4-5" wide up to 1-2 inches deep. The retention of much of the adherent coating, from heat to heat, using formulation E is markedly better than with formulation A. Formulation C largely fails to coat the walls of the ingots and no adherent coating results from treatment with the conventional mold coating.

The ability of the coatings produced by formulation E of this invention to consistently fill large cracks and holes in the used and well worn molds accounts for the greatly superior mold life resulting from the use of a typical composition of this invention. The retention, from heat to heat, of the coating on the interior surfaces of the ingot mold resulting from the use of Formula E, also largely prevents the formation of cold shuts, which are a common occurrence in ingots treated with the other formulations. Splashed molten metal droplets, which usually cause cold shuts upon contact and solidification on the sides of an ingot mold during teeming, are observed to fall back into the molten metal upon contact with the residual coating when using Formula E. This occurs because the coating remaining on the ingot mold from prior heats is readily melted by the molten metal droplets, thus allowing the droplets to fall back into the molten metal and minimize the formation of cold shuts. The almost complete elimination of splash metal defects (e.g., cold shuts) and the repair or smoothing over of harmful cracks and holes in the surface of both the used and well worn molds is largely responsible for the unique improvement in the ingot-to-billet yields obtained for this test series as compared with the control ingots and other ingots treated With prior art exothermic mold additives. The lack of substantial improvement in the ingot-to-billet yields with Formulas A, C, and K, beyond those for the ingot molds with a treatment of a conventional mold coating, or when compared with the significant improvements of an exothermic formula of this invention, is indicative of the superiority of formulation E, typical of this invention, over prior art exothermic mold additive formulatrons.

An additional advantage of formulation E over the conventional mold coating is found in the elimination of the mold conditioning and handling required when such mold coatings are used. No mold conditioning or transporting is required for the molds treated with Formula E other than the removal (by vacuum cleaner) of occasional pieces of scale and coating which are usually found in the bottom of the mold.

The superior results obtained with formulation E, representative of the formulations of this invention, in ingotto-billet yields is also obtained when end products are bars, tubing, slab and sheet products.

The exothermic compositions of the present invention are individually made by either mechanical mixing of all specified components or by mixing the reducing agent and the boron-containing compound with products resulting from the fusion of the remaining components. In mechanical mixing the individual components are combined as a dry mix which may then be briquetted, extruded, or tabletted, using conventional agglomerating agents. However, to improve the stability of final tablets of exothermic compositions during storage and shipping, it is often desired to fuse some of the components, for example, the soda ash, with the oxidizing agent, such as iron oxide, titanium dioxide or ilmenite in an oxidizing atmosphere. The fused components, after size reduction, are then mixed directly with the remaining components of the exothermic composition and tabletted, extruded or briquetted, as desired.

p 10 EXAMPLE 6 Using dry raw materials in the 20 mesh and smaller size range, the following quantities, plus 1 lb. of stearic acid, are weighed out and blended for 15 minut s in a muller type mixer:

Lb. Ilmenite (essentially FeO'TiO 63.2 Anhydrous sodium carbonate 20.0 30-35% calcium-silicon powder 10.7 Anhydrous sodium tetraborate 6.0

After blending 12 lb. of dilute sodium silicate solution (83% N brand sodium silicate, 17% distilled water) is added as a binder and an additional 10 minutes of mixing occurs. In general, the binder, sodium silicate or a polyvinyl alcohol, is used at 4% to 20% by Weight of raw mixture. The damp, puddled mixture is then dried for 10 minutes in a forced air electric oven at 240 F. The product is, however, equally well obtained by air cooling. The dry material is granulated in an oscillating granulator using a 12 to 16 mesh screen. Tablets, /2" diameter, A thick and weighing approximately 2 grams each, are produced in a rotary tablet machine at the rate of 1,000 grams/minute using approximately 2,000 p.s.i. to 40,000 p.s.i. compaction pressure applied at the punches. The tablets are dried for at least 3 hours in a forced air, steam heated, tray oven at 240 F. The weight loss on drying is generally in the range of l-4%. Compaction lubricants, such as talc and inorganic stearates, e.g., stearic acid and lithium stearate, may also be used in quantities ranging from 0.3% to 2% by weight of dry raw materials.

Variations of the above process include the addition by blending of 3% to 15% by weight on a dry raw material basis of binder solution or fluid to yield a mixture that will agglomerate readily. Such agglomerates are then compacted under pressure ranging from 2,000 p.s.i. to 40.000 p.s.i. Pellets of the compositions of this invention, ranging in size from diameter x A" long to 1 /2" diameter x 1 /2" long are also useful as mold additives. It is understood that briquetting as well as extrusion and other types of pelletizing equipment can be used to produce pellets useful in the practice of this invention.

The above composition is found to be highly exothermic and useful as a mold additive in casting stainless steel ingots. This composition is similar to composition E of Tables 2 and 3, and yields similar results.

EXAMPLE 7 A partial fusion step is used in the preparation of an exothermic composition by first fusing 44.7 pounds of anhydrous sodium carbonate with 33.8 pounds of iron oxide at about 850-1,100 C. in an oxidizing atmosphere. The fused mass is cooled, crushed and ground to approximately 35 mesh and mixed with elemental calcium and silicon together with anhydrous sodium tetraborate to yield a product of the following proportions in percent by weight:

Percent Fusion product (from 44.7 lb. anhydrous sodium carbonate plus 33.8 lb. iron oxide, Fe O 70.0 Calcium 8.0 Silicon 16.0 Anhydrous sodium tctraborate 6.0

The fusion product indicated above was identified as sodium perferrate, Na FeO by X-ray diffraction analy- SIS.

The present formulation, in the range of Type G compositions shown in Table 2, is particularly useful as a mold additive in casting steel ingots. For example, in casting C 1020 carbon steel, with 11 pounds of the exothermic formulation per ton of steel, the steel surface is found to be unusually smooth (Stringer Index of 11 1 and Ingot Cleanliness Index of 1) and to give very little smoke (Smokiness Index of 2).

EXAMPLE 8 The method of Example 7 is used to prepare the following composition, shown in percent by weight, which yields the same results as for Example 7 when used in the casting of stainless steel:

Percent Fusion product 53.2 Titania (the fusion product and titaria are obtained from fusion of 59.5 lb. ilmenite and 45.5 lb. anhydrous sodium carbonate) 21.4 Calcium 15.7 Silicon 3.9

Anhydrous sodium tetraborate 5.7

In this case, initial fusion of anhydrous sodium carbonate with ilmenite in the above quantities is accomplished instead of using the quantities and components indicated in Example 7. The fusion product indicated above is identified as essentially NaFeO by X-ray diffraction analysis.

What is claimed is:

1. An exothermic metallurgical composition including a reducing agent selected from the group consisting of calcium and silicon mixtures in which from 20% to 80% by weight of said mixture is calcium, an oxidizing agent selected from the group consisting of iron oxides, titanium oxides, and ilmenite, together with a boron compound selected from the group consisting of boron oxides, boric acid, sodium borates and potassium borates.

2. An exothermic metallurgical composition comprising a reducing agent selected from the group consisting of calcium and silicon mixtures containing 20% to 80% by weight of calcium, said reducing agent being present in the range of from 10% to 40% by weight, and an oxidizing agent selected from the group consisting of iron oxides, titanium oxides, and ilmenite, the said oxidizing agent being present in the range of from 20% to 70% by weight, and the remainder being at least one boron compound selected from the group consisting of boron oxide, boric acid, sodium borates, and potassium borates, the said boron compounds being present as equivalent amounts of B in the range of above 2 and below 62 parts per 100 parts by weight of mixed oxides, consisting of the equivalent oxides of the titanium, iron, sodium, and potassium compounds, excluding boroncontaining compounds, present in the composition.

3. An exothermic metallurgical composition comprising a reducing agent selected from the group consisting of calcium and silicon mixtures containing 20% to 80% by weight of calcium, said reducing agent being present in the range of from to 36% by weight, and an oxidizing agent selected from the group consisting of iron oxides, titanium oxides, and ilmenite, the said oxidizing agent being present in the range of from 23% to 66% by weight, and the remainder being at least one boron compound selected from the group consisting of boron oxide, boric acid, sodium borates, and potassium borates, the said boron compounds being present as equivalent amounts of B 0 in the range of above 2 and below 45 parts per 100 parts by weight of mixed oxides, consisting of the equivalent oxides of the titanium, iron, sodium, and potassium compounds, excluding boron-containing compounds, present in the composition.

4. An exothermic metallurgical composition comprising a reducing agent selected from the group consisting of calcium and silicon mixtures containing to 80% by weight of calcium, said reducing agent being present in the range of from 10% to 31% by weight, and an oxidizing agent selected from the group consisting of iron oxides, titanium oxides, and ilmenite, the said oxidizing agent being present in the range of from 25% to 64% by Weight, and the remainder consisting of at least one boron compound selected from the group consisting of boron oxide, boric acid, sodium borates, and potassium borates, the said boron compounds being present as equivalent amounts of B 0 in the range of above 2 and below 37 parts per 100 parts by weight of mixed oxides, consisting of the equivalent oxides of the titanium, iron, sodium, and potassium compounds, excluding boron-containing compounds, present in the composition.

5. An exothermic metallurgical composition comprising as a reducing agent, a calcium-silicon mixture corresponding to the formula Ca Si said reducing agent being present in the range of from 10% to 40% by weight, and an oxidizing agent selected from the group consisting of iron oxides, titanium oxides, and ilmenite, the said oxidizing agent being present in the range of from 20% to 70% by weight, and the remainder consisting of at least one boron compound selected from the group consisting of boron oxide, boric acid, sodium borates, and potassium borates, the said boron compounds being present as equivalent amounts of B 0 in the range of above 2 and below 62 parts per 100 parts by weight of mixed oxides, consisting of the equivalent oxides of the titanium, iron, sodium, and potassium compounds, excluding boron-containing compounds, present in the composition.

6. An exothermic metallurgical composition comprising a mixture of the following components, expressed as approximate percentage by weight:

Ilmenite (essentially FeO-TiO 63.2 Anhydrous sodium carbonate (Na CO 20.0 30-35% calcium-silicon 10.7 Anhydrous sodium tetraborate (Na B O- 6.0

7. An exothermic metallurgical composition comprising a mixture of the following components, expressed as approximate percentage by weight:

said fusion product indicated above is identified as sodium perferrate, Na FeO by X-ray diffraction analysis.

8. A process for the manufacture of an exothermic metallurgical composition consisting of a reducing agent selected from the group consisting of calcium and silicon mixtures containing 20% to by weight of calcium, said reducing agent being present in the range of from 10% to 40% by weight, and an oxidizing agent selected from the group consisting of iron oxides, titanium oxides, and ilmenite, the said oxidizing agent being present in the range of from 20% to 70% by weight, and the remainder being at least one boron compound selected from the group consisting of boron oxides, boric acid, sodium borates, and potassium borates, the said boron compounds being present as equivalent amounts of B 0 in the range of above 2 and below 62 parts per parts by weight of mixed oxides, consisting of the equivalent oxide of the titanium, iron, sodium, and potassium compounds, excluding boron-containing compounds, present in the composition, the process comprising admixing the said components in particulate form, and compacting the same at a pressure ranging from 2,000 p.s.i. to 40,000 p.s.i. to obtain tablets or pellets of the resulting exothermic composition.

References Cited in the file of this patent UNITED STATES PATENTS 2,481,599 Kinzel et al Sept. 13, 1949 3,025,153 Cross Mar. 13, 1962 3,072,985 Ahmansson et al Jan. 15, 1963 3,089,767 Rinesch May 14, 1963 UNITED STATES'PATENT 0EE1cE CERTIFICATE OF CORRECTION Patent No 5 ,153 ,605 October 20 1964 Courtland M. Henderson et a1 ears in the above numbered pat- It is hereby certified that error app d Letters Patent should read as ent requiring correction and that the sai corrected below.

e 1, first column, line 16 thereof for Column 3, Tabl column 4, Table 2, first column, line 15 PeO read Pe thereof for (Na B 0 read (Na B O column 10, line 38, for 40.000" read 40,000

Signed and sealed this 22nd day of March 1966 (SEAL) Attest:

ERNEST W. SWIDER Attesting Officer EDWARD 1. BRENNER Commi sioner of Patents UNITED STATES 'PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,153,605 October 20, 1964 Courtland M. Henderson et a1.

certified tha-t error appears in the above numbered pat- It is hereby t the said Letters Patent should read as ent requiring correction and tha corrected below.

line 16 thereof, for

Column 3, Table 1, first column,

line 15 "FeO read FeO column 4, Table 2, first column,

thereof, for "(Na B O read (Na B O column 10, line 38 for "40 000" read 40,000

Signed and sealed this 22nd day of March 1966.

( L) Attest:

ERNEST W. SW'IDER Attesting Officer EDWARD J. BRENNER Commissioner of Patents

Claims (1)

1. AN EXOTHERMIC METALLURGICAL COMPOSITION INCLUDING A REDUCING AGENT SELECTED FROM THE GROUP CONSISTING OF CALCIUM AND SILICON MIXTURES IN WHICH FROM 20% TO 80% BY WEIGHT OF SAID MIXTURE IS CALCIUM, AN OXIDIZING AGENT SELECTED FROM THE GROUP CONSISTING OF IRON OXIDES, TITANIUM OXIDES, AND ILMENITE, TOGETHER WITH A BORON COMPOUND SELECTED FROM THE GROUP CONSISTING OF BORON OXIDES, BORIC ACID, SODIUM BORATES AND POTASSIUM BORATES.